Service Providers (SPs) use Wide Area Networks (WANs) and Metropolitan Area Networks (MANs) to provide customers with connectivity to the Internet and/or with connectivity to geographically diverse customer locations. Historically, WANs and MANs have been implemented using Synchronous Optical Networks (SONET), Frame Relay, or Asynchronous Transfer Mode (ATM) technologies. Recently, however, Service Providers have begun to use Ethernet technology to implement WANs and MANs. Such implementations use Ethernet as the frame format to connect the subscriber's equipment, called a Customer Edge (CE) device, to the network. Alternatively, such implementations can involve encapsulating an Ethernet frame according to one of several other protocols (or vice versa) to achieve the transfer of the Ethernet frame from the CE device to the Service Provider's network. The point of demarcation between the CE device and the Service Provider's network is referred to as the User-to-Network Interface (UNI).
Ethernet Virtual Connections (EVCs) provide the fundamental connectivity mechanism for Ethernet-based MAN and WAN service. An EVC associates a group of UNIs. The UNIs coupled by the same EVC form a closed user group, such that Ethernet frames entering the EVC at one UNI can only exit the network at another UNI that is associated with the same EVC.
EVCs can be point-to-point, multipoint-to-multipoint, or rooted-multipoint. Point-to-point EVCs couple exactly two UNIs. Multipoint-to-multipoint EVCs can associate more than two UNIs. When a multipoint EVC is used, a single Ethernet frame that enters the multipoint EVC at one UNI can be replicated within the Service Provider network, such that copies of that Ethernet frame exit the network at multiple other UNIs (e.g., if multicast transmission is desired) or at all of the other UNIs (e.g., if broadcast transmission is desired) associated by that EVC. A rooted-multipoint EVC designates each UNI coupled by that rooted-multipoint EVC as either a root or a leaf. Traffic entering an EVC at a root UNI can be sent to any or all of the other UNIs associated by the EVC; however, traffic entering an EVC at a leaf UNI can only be sent to root UNIs associated by the EVC.
A customer wishing to create a topology using an Ethernet-based WAN or MAN can connect a device such as an Internet Protocol (IP) router at each of a number of UNIs and associate an IP subnet with each of the available EVCs. In such a situation, control and provisioning of EVCs in the network are under the administrative control of the Service Provider (SP), while the configuration of the router is under the customer's administrative control. This split in administrative domains can lead to a number of challenges. At the most practical level, the split requires the SP and customer to coordinate their efforts and (even if attempts are made to coordinate) a number of potential problems, including mis-configurations, confusion about when service will become active, and the like, may arise. To reduce the likelihood of these problems, it is desirable to decouple, as much as is possible, the configuration tasks of the SP from the configuration tasks of the customer.
While the invention is susceptible to various modifications and alternative forms, specific embodiments of the invention are provided as examples in the drawings and detailed description. It should be understood that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. Instead, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.